Histology Fact Sheet: Thyroid

Anatomy of the Thyroid Gland

The thyroid gland is located in the neck. It lies just below the larynx.  A thin capsule surrounds the thyroid gland. The thyroid gland is made of two lobes. The two lobes of the thyroid are connected by the isthmus.  The thyroid gland is a very vascular gland. 

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Histology of the Thyroid Gland

Upon examining the histology, it can be seen that the thyroid gland is composed of follicles.

Follicles are lined by a single layer of epithelial cells.  They are filled with an amorphous colloidal material.

There are two cell types in the thyroid gland: follicular cells and parafollicular cells. Follicular cells release and store thyroid hormone. Parafollicular cells of the thyroid gland are also called C cells. The parafollicular cells secrete calcitonin.

Histology slide of thyroid
Histology slide courtesy of Education Interactive Histology Photo CD

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Hormones of the Thyroid Gland

The thyroid gland secretes the thyroid hormones (T3 and T4) and calcitonin.

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Histology: A Text and Atlas
Michael H. Ross/Edward J. Reith